title: Track structure based modelling of chromosome aberrations after photon and alpha-particle irradiation.
abstract: A computational model of radiation-induced chromosome aberrations in human cells within the PARTRAC Monte Carlo simulation framework is presented. The model starts from radiation-induced DNA damage assessed by overlapping radiation track structures with multi-scale DNA and chromatin models, ranging from DNA double-helix in atomic resolution to chromatin fibre loops, heterochromatic and euchromatic regions, and chromosome territories. The repair of DNA double-strand breaks via non-homologous end-joining is followed. Initial spatial distribution and complexity, diffusive motion, enzymatic processing, synapsis and ligation of individual DNA ends from the breaks are simulated. To enable scoring of different chromosome aberration types resulting from improper joining of DNA fragments, the repair module has been complemented by tracking the chromosome origin of the ligated fragments and the positions of centromeres. The modelled motion of DNA ends has sub-diffusive characteristics and corresponds to measured chromatin mobility within time-scales of a few hours. The calculated formation of dicentrics after photon and α-particle irradiation in human fibroblasts is compared to experimental data (Cornforth et al., 2002, Radiat Res 158, 43). The predicted yields of dicentrics overestimate the measurements by factors of five for γ-rays and two for α-particle irradiation. Nevertheless, the observed relative dependence on radiation dose is correctly reproduced. Calculated yields and size distributions of other aberration types are discussed. The present work represents a first mechanistic approach to chromosome aberrations and their kinetics, combining full track structure simulations with detailed models of chromatin and accounting for the kinetics of DNA repair.
authors.affiliation: Helmholtz Zentrum München - German Research Center for Environmental Health, Institute of Radiation Protection, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany. Electronic address: friedland@helmholtz-muenchen.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Friedland
authors.forename: Pavel
authors.initials: P
authors.lastname: Kundrát
mesh_terms: D000512:Alpha Particles / Q000009:adverse effects*; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000528:radiation effects; D002869:Chromosome Aberrations / Q000528:radiation effects*; D003198:Computer Simulation; D004249:DNA Damage / Q000235:genetics / Q000528:radiation effects; D004260:DNA Repair / Q000235:genetics / Q000528:radiation effects; D005347:Fibroblasts / Q000166:cytology / Q000528:radiation effects*; D005720:Gamma Rays / Q000009:adverse effects*; D006801:Humans; D018499:Linear Energy Transfer; D009010:Monte Carlo Method; D017785:Photons / Q000009:adverse effects*; D011829:Radiation Dosage; D012867:Skin / Q000166:cytology / Q000528:radiation effects*
chemical_list: D002843:Chromatin
keywords: Chromosome aberrations; DNA damage repair; Mathematical modelling; Monte Carlo simulation; Radiation track structure